I am asking about a Jew. He is 100% materialist, atheist in his world view.
He keeps the most basic laws of Judaism: keeps Sabbath (not so strictly as Orthodox Jews do, but keeps), doesn't eat pork and doesn't mix milk and meat. (I don't know if he has brith, but I am nearly sure, that he has.) Not every weekend, but he is a regular visitor in a local synagogue.
I think, he does it because although he doesn't believe the religion, he wants to honor his religious friends and ancestors. Furthermore, this is the way of life he is accustomed to.
I think it would be nicer if he would do what God wants from him. But, somewhere I've read, that Judaism is more like law as simply a religion. And he keeps the law on a basic level.
So, what will happen to a Jew, keeping basic laws, but not believing anything over the pure matter?